An encoding method includes determining a target adaptive broadening factor based on a quantized line spectral frequency (LSF) parameter of a primary channel signal in a current frame and an LSF parameter of a secondary channel signal in the current frame, and writing the quantized LSF parameter of the primary channel signal in the current frame and the target adaptive broadening factor into a bitstream.
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2. The stereo signal encoding method of claim 1, further comprising determining a second quantized LSF vector of the secondary channel signal based on the target adaptive broadening factor and the first quantized LSF vector.
5. The stereo signal encoding method of claim 1, further comprising determining that the LSF vector meets a reusing condition.
This invention relates to stereo signal encoding, specifically improving efficiency by reusing linear spectral frequency (LSF) vectors. The problem addressed is the computational and memory overhead in encoding stereo audio signals, where redundant LSF vector calculations occur when similar spectral characteristics exist between left and right channels. The solution involves determining whether an LSF vector meets a reusing condition, allowing the encoder to reuse previously computed LSF vectors instead of recalculating them. This reduces processing load and memory usage while maintaining audio quality. The method includes analyzing spectral data to identify conditions where LSF vectors can be shared between channels, such as when spectral differences fall below a predefined threshold. By reusing LSF vectors, the encoding process becomes more efficient, particularly in scenarios with limited computational resources or high encoding demands. The invention is applicable to audio codecs and real-time communication systems where efficient stereo encoding is critical.
7. The stereo signal decoding method of claim 6, further comprising converting the first quantized LSF vector to obtain linear prediction coefficients.
9. The stereo signal encoding apparatus of claim 8, wherein the instructions further cause the stereo signal encoding apparatus to be configured to determine a second quantized LSF vector of the secondary channel signal based on the target adaptive broadening factor and the first quantized LSF vector.
13. The stereo signal decoding apparatus of claim 12, wherein the instructions further cause the stereo signal decoding apparatus to be configured to convert the first quantized LSF vector to obtain linear prediction coefficients.
14. The stereo signal decoding apparatus of claim 13, wherein the instructions further cause the stereo signal decoding apparatus to be configured to modify the linear prediction coefficients based on the target adaptive broadening factor to obtain modified linear prediction coefficients.
15. The stereo signal decoding apparatus of claim 14, wherein the instructions further cause the stereo signal decoding apparatus to be configured to convert the modified linear prediction coefficients to obtain a converted LSF vector, and use the converted LSF vector as the broadened LSF vector.
This invention relates to stereo signal decoding, specifically improving the quality of decoded audio signals by modifying linear prediction coefficients to broaden the spectral envelope. The problem addressed is the degradation of stereo audio quality when decoding signals, particularly in scenarios where spectral details are lost or distorted during compression or transmission. The apparatus includes a processor and memory storing instructions that, when executed, perform operations to decode a stereo signal. The instructions cause the apparatus to obtain linear prediction coefficients from the stereo signal, modify these coefficients to broaden the spectral envelope, and convert the modified coefficients into a line spectral frequency (LSF) vector. The converted LSF vector is then used as the broadened LSF vector to enhance the decoded audio's spectral characteristics. The modification process ensures that the spectral envelope is widened, improving the perceived audio quality by reducing artifacts and enhancing spatial perception. The apparatus may also include additional components for further processing, such as filtering or equalization, to refine the decoded signal. The invention aims to provide a more natural and immersive stereo audio experience by dynamically adjusting the spectral envelope during decoding.
16. The stereo signal decoding apparatus of claim 15, wherein the instructions further cause the stereo signal decoding apparatus to be configured to use the converted LSF vector as the broadened LSF vector.
A stereo signal decoding apparatus processes audio signals to enhance spatial perception. The apparatus converts a line spectral frequency (LSF) vector, which represents spectral characteristics of an audio signal, into a modified form to improve stereo decoding. The conversion process broadens the LSF vector to create a broader spectral representation, which enhances the perceived stereo width of the decoded audio. The apparatus then uses this broadened LSF vector directly as the final output for further audio processing. This approach ensures that the decoded stereo signal maintains a natural and immersive spatial quality, addressing the challenge of preserving audio clarity while expanding the perceived stereo image. The apparatus may include a processor and memory storing instructions that, when executed, perform the LSF vector conversion and broadening. The method involves analyzing the original LSF vector, applying a broadening algorithm to adjust its spectral characteristics, and integrating the modified vector into the stereo decoding pipeline. This technique is particularly useful in applications requiring high-fidelity stereo reproduction, such as virtual reality, gaming, and high-end audio systems. The apparatus ensures that the broadened LSF vector accurately represents the intended stereo effect without introducing artifacts, improving the overall listening experience.
17. The stereo signal encoding method of claim 5, wherein determining that the LSF parameter meets the reusing condition includes determining whether a distance between an LSF vector of the primary channel signal and the LSF vector of the secondary channel signal is less than or equal to a threshold.
18. The stereo signal decoding method of claim 7, further comprising modifying the linear prediction coefficients based on the target adaptive broadening factor to obtain modified linear prediction coefficients.
19. The stereo signal decoding method of claim 18, further comprising converting the modified linear prediction coefficients to obtain a converted LSF vector, wherein the converted LSF vector is the broadened LSF vector.
This invention relates to audio signal processing, specifically stereo signal decoding techniques for enhancing audio quality. The method addresses the challenge of accurately reconstructing stereo audio signals from encoded data, particularly when dealing with linear prediction coefficients that may require broadening to improve perceptual quality. The technique involves modifying linear prediction coefficients to broaden their spectral characteristics, which helps in achieving a more natural and spatially expanded sound reproduction. The modified coefficients are then converted into a line spectral frequency (LSF) vector, which represents the broadened spectral characteristics. This conversion step ensures that the decoded stereo signal maintains high fidelity and spatial accuracy. The broadening of the LSF vector is crucial for improving the perceived width and depth of the stereo image, addressing common issues in encoded audio where spectral details may be compressed or distorted. The method is particularly useful in applications such as audio codecs, virtual reality audio systems, and high-definition audio playback, where accurate spatial rendering is essential. By dynamically adjusting the LSF vector, the technique ensures that the decoded stereo signal retains its original spatial attributes while minimizing artifacts. The overall approach enhances the listener's experience by providing a more immersive and natural audio reproduction.
20. The stereo signal decoding method of claim 19, wherein the converted LSF vector is used as the broadened LSF vector.
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December 28, 2020
November 15, 2022
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